Electronic phase diagram of CeFeAsO as a function of hydrostatic pressure and As by P substitution

We present a local probe study of the electronic properties of hydrostatic and chemical (due to As by P substitution) pressure in CeFeAsO by means of energy- and time-domain Mössbauer spectroscopy. The application of pressure results in a compression of the unit cell. We investigated the magnetic hyperfine field, the electric field gradient, and the electron density at the Fe nucleus. We found a distortion of the FeAs tetrahedra with increased P-substitution level while it remains unchanged in the case of hydrostatic pressure. We observed a nearly linear suppression of the magnetic hyperfine field to zero between 0 and 40 % P-substitution level while the field is reduced by 25 % between 0 and 4.5 GPa followed by an abrupt decrease to zero at 5.2 GPa.